As this document indicates, the video settings will depend on the iPod model. All iPods supporting video (except for the iphone/ipod touch) export XML data describing the video formats they support, see
http://www.ipodlinux.org/wiki/Device_Information and grep for "VideoCodec" for an example of what kind of information is available on the iPod. Dunno if that's enough to build a device profile or not.. If that's enough and if you think libgpod should export this information, let me know exactly how you'd like it to be done ;)
Christophe